It has been proposed that 3,4-dialkoxy styrenes (substituted styrenes) be prepared by dehydrohalogenating chloro-1-(3,4-dialkoxyphenyl)ethanes using pyridine as the dehydrohalogenating reagent. In the prior art, 3,4-(dimethoxy)styrenes have also been prepared by the thermal dehydration of 1-(3,4-dimethoxyphenyl)ethanol and by methylation of 4-hydroxy-3-methoxy styrene with methyl iodide or dimethyl sulfate. These methods have not been entirely satisfactory because the yields are rather low. Very low yields are obtained in the dehydrohalogenation process because of the formation of the quaternary salt of pyridine with the chloro compound. The thermal dehydration process is also relatively expensive because of the high temperature required for the reaction.
It has also been proposed that haloalkyl styrenes be prepared by at least partially dehydrohalogenating halogenated haloalkylphenyl ethanes using pyridine as the dehydrohalogenating reagent. These styrenes have also been prepared by haloalkylating styrene. The same disadvantages that the use of pyridine presents in its use in preparing dialkoxy styrenes occur in such methods.